In the 70s I spent a fair amount of time scrounging the scrap yards in the Detroit area. (the source of my Chevy aluminum 283 and 427blocks) On one occasion I noticed huge piles of GM Wankle engines and took a closer look. They were designed to bolt to the standard Chevy bell housing and had standard alternators and other external pieces. I left thinking the decision to cancel the program came very close to production.
(other interesting pieces that I saw were Chrysler turbines)
Paul